Creases stamped into a material layer form folding lines, for example, for the production of envelopes, mailing sleeves or packaging articles of other kinds. The material layer employed can consist of paper, plastic or other elastically and plastically deformable materials. Normally, such a material layer is present in the form of a web having a specifically prescribed width and layer thickness, or else as a blank having a specifically prescribed format. As a rule, stamping a variable number of creases into such a material layer is one of several process steps in a processing chain. For instance, in the production of envelopes, the height of the envelopes is defined by the distance of creases that are adjacent to each other. Other process steps encompass especially cutting and folding processes.
When creases are stamped into a material layer, the latter is usually guided through a lengthwise gap between a creasing roller having two creasing blades and a counter roller fitted with an elastic covering that rolls against this creasing roller. Within the scope of the rolling motion, with every revolution of the creasing roller, the creasing blades generally stamp two creases into the material layer perpendicular to the direction of rotation, and the distance of these creases corresponds to the distance between the creasing blades along the circumference of the creasing roller. Such a device with a creasing roller and a counter roller is disclosed in German patent application DE 196 400 42 A1.
In order to vary the creasing distance, for example, if the format height for envelopes or mailing wrappers changes, the two creasing blades have to be adjusted with respect to each other. For this purpose, one of the creasing blades is arranged stationary on the creasing roller while the other creasing blade is arranged on a segmented tray that can be adjusted in the creasing roller. With this construction, a segment-shaped gap is formed in the creasing roller, and the circumferential extension of the gap is determined by the difference between the minimum and the maximum of the adjustable circumferential distance of the creasing blades. The position of the adjustable segmented tray can be varied within this gap. One disadvantageous aspect of this is that residual gaps of variable sizes remain. These gaps each have to be filled up with additional segmented elements so that the creasing roller on whose outer surface the web of material is being transported has a radius that is essentially constant in all directions orthogonally to the longitudinal axis, and so as to compensate for an unbalance of the creasing roller that would be caused by a change in the position of the segmented tray. Owing to these design-related drawbacks, changing the format is very time-consuming and laborious.
An object of the present invention is to provide a device to stamp a number of creases into a material layer by means of which the format of the creasing distance can be changed with very little effort.